(1) Field of the Invention
The present invention relates to a system and method for controlling a vehicle speed to a desired cruise speed in which a power supply to the automatic cruise speed controlling system is inhibited when the vehicle speed is below a predetermined value.
(2) Background of the Art
A Japanese Patent Application First Publication (Unexamined) sho 59-58134 published on Apr. 3 , 1984 exemplifies one of previously proposed systems for automatically controlling a vehicle speed to a desired cruise speed in which when a vehicle is accelerated, the vehicle speed arrives at a desired speed, and a driver depresses a cruise speed setting button, an opening angle of an engine throttle valve or carburator is adjusted so that the vehicle speed coincides with the set cruise speed without operation of an accelerator pedal. Therefore, it is convenient for the driver to run the vehicle without operation of the accelerator pedal in a case where the vehicle runs on a freeway.
The operations of such automatic cruise controlling systems are inhibited when a clutch pedal or brake pedal is depressed and when the accelerator pedal is again depressed so that the vehicle speed exceeds the set cruise speed. In this last instance, if depression of the accelerator pedal is halted, the vehicle speed is decreased due to an engine braking and the vehicle speed returns to the set cruise speed. At this time, the vehicle speed can run at the set cruise speed.
However, in such previously proposed automatic cruise speed controlling systems, power supply switches for the systems can always be turned on when ignition switches of the vehicles are in the ON states. Therefore, if the drivers erroneously turn on the power switches when the vehicles stop or run at a low speed at which no automatic cruise control is needed, power is wastefully supplied to the systems.